Optical recording medium

ABSTRACT

According to the present invention, there is provided an optical recording medium including at least an information recording layer and a reflective film in which the reflective film is comprised of an AgCu alloy thin film containing Cu the content of which is greater than or equal to 3.0 [atomic %] and less than or equal to 6.5 [atomic %]. Thus, the optical recording medium can be made inexpensive and weather resistance of the optical recording medium can be improved, thereby making it possible to avoid characteristics of the optical recording medium from being deteriorated even after it has been stored for a long time.

TECHNICAL FIELD

[0001] The present invention relates to an optical recording medium,such as a CD (Compact Disc) or a CD-ROM (CD-Read Only Memory), in whicha translucent reflective film and a reflective film can be improved inweather resistance more and which can be manufactured moreinexpensively.

BACKGROUND ART

[0002] As optical recording medium for recording a variety ofinformation such as audio information and video information, varioustypes of optical recording mediums are available in the form of aread-only optical recording medium such as a CD and a CD-ROM, arewritable optical recording medium such as a magneto-optical disk and aphase-change optical disc and a write-once optical disc such as a CD-Rmade of an organic material.

[0003] Information recording layers comprising these optical recordingmediums are indented to form thereon very small indentations such asphase pits and pregrooves to record data information, a tracking servosignal and the like.

[0004] Recently, there is an increasing demand for realizing opticalrecording medium capable of recording a larger amount of information,and a DVD (Digital Versatile Disc) of a two-layer structure havinglaminated first and second information recording layers, for example,becomes commercially available.

[0005]FIG. 4 is a schematic cross-sectional view illustrating an opticalrecording medium 200 of a two-layer structure in which a firstinformation recording layer 231 and a second information recording layer232 are laminated to each other.

[0006] In the first information recording layer 231, a translucentreflective film 223 made of a suitable material, such as Au, Si, AgPdCuand AgPdTi, is deposited on first very small indentations 211 which areformed at the same time a first substrate 201 is molded by injectionmolding.

[0007] In the second information recording layer 232, a reflective film224 composed of a suitable thin film such as an Al thin film and an Alalloy thin film, is deposited on second very small indentations 222which are formed at the same time a second substrate 202 is molded byinjection molding.

[0008] A transparent adhesive layer 203 laminates the first and secondsubstrates 201 and 202 with the first and second information recordinglayers 231 and 232 being facing to each other to form a two-layerinformation recording layer.

[0009] It is desirable that a set of optical heads should be used toreproduce or record or to reproduce and record (hereinafter simplyreferred to as “reproduce or record”) information from the first andsecond information recording layers 231 and 232 of the optical recordingmedium 200 with irradiation of laser beams from the same side of theoptical recording medium, e.g., from the first substrate 201 side, forexample, so that a drive apparatus therefor can be simplified, theoptical heads can access these information recording layers 231 and 232in a short time and can continuously record or reproduce theseinformation recording layers.

[0010] When the optical head irradiates laser beams on the first andsecond information recording layers 231 and 232 from the same side ofthe optical recording medium to record or reproduce or record andreproduce the first and second information recording layers, the sameoptical head focuses a laser beam L on the first information recordinglayer 231 to record or reproduce or record and reproduce the firstinformation recording layer 231 as shown by a solid line in FIG. 4 andthe same optical head focuses a laser beam L on the second informationrecording layer 232 to record or reproduce or record and reproduce thesecond information recording layer 232 as shown by a dotted line in FIG.4.

[0011] In order that the same optical head may record or reproduce orrecord and reproduce the first and second information recording layers231 and 232 with irradiation of laser beams, the first informationrecording layer 231 has the translucent reflective film 223 formed atits entrance side for inward laser beams to reflect part of irradiatedlaser beams so that the first information recording layer 231 may berecorded or reproduced and to pass part of laser beams to allow part oflaser beams to travel to the second information recording layer 232 sothat the second information recording layer 232 may be recorded orreproduced.

[0012] The transparent adhesive layer 203, made of an adhesive materialhaving a high transmittance with respect to laser beams, laminates thefirst and second information recording layers 231 and 232 with adistance long enough to prevent their reproduced signal from interferingwith each other. Therefore, the optical heads can adjust objectivelenses so as to properly focus the laser beams on the positionscorresponding to the respective information recording layers 231 and232, thereby making it possible to reproduce information from therespective information recording layers with high accuracy.

[0013] Design of films of the translucent reflective film 223 of thefirst information recording layer becomes extremely important to realizethe above-mentioned signal reproducing method.

[0014] Au, Si, AgPdCu and AgPdTi are used as materials for forming thetranslucent reflective film 223 as described above.

[0015] So far these materials have been used as the materials of thetranslucent reflective film because they can satisfy opticalcharacteristics of the translucent reflective film 223 from a standpointof reflectance and transmittance relative to laser beams and they can beeasily deposited as thin films by sputtering.

[0016] However, Au encounters with a problem in which costs of materialsincrease. Although Si is relatively inexpensive, it is poor in adhesiveproperty with which it is bonded to the adhesive material comprising thetransparent adhesive agent layer 203 or it is bonded to the material ofthe substrate 201. Accordingly, silicon is not sufficiently reliable inmechanical deformation such as bending or warping or under severecircumstances with high humidity.

[0017] Further, when the Si film is compared with metal thin films, Siis easily separated from the inside of a sputtering chamber where it isstuck in the sputtering process when the film is deposited, i.e.,so-called particles are easily produced so that an error rate is causedto be degraded.

[0018] The translucent reflective film needs a film thickness rangingfrom 5 [nm] to 25 [nm] when it is made of metals or Si semiconductormaterials and so on that have been so far used to form ordinarytranslucent reflective films. This film thickness of the translucentreflective film is thin as compared with a film thickness ranging from35 [mm] to 60 [nm] of a reflective film of an ordinary compact disc, forexample. The metals or the Si semiconductor materials and the like foruse in the ordinary translucent reflective film are easily oxidized attheir surface by influences exerted from the substrate 201 side afterthey have been stored for a long time and further after they have beenstored under circumstances with high temperature and high humidity.Accordingly, oxidation produced on the surface changes a reflectance ofthe translucent reflective film having such film thickness considerably,and this translucent reflective film is poor in weather resistance.

[0019] The translucent reflective film 223 is damaged not only by theinfluence from the substrate 201 side but also by oxidation from acontact portion where it is brought in contact with the transparentadhesive agent layer 203. The oxidation from the contact portion changesthe reflectance of the translucent reflective film and deteriorates thejitter of the reproduced signal unavoidably.

[0020] Apart from the problem of the above-mentioned oxidation, thetranslucent reflective film encounters with a phenomenon in which atomsare caused to move within the deposited film to increase thermalconductivity or reflectance of the translucent reflective film after thetranslucent reflective film has been left under circumstances with hightemperature where so-called annealed effect happens. This phenomenonbecomes a serious problem depending upon compositions of the translucentreflective film.

[0021] The optical recording medium having the multilayer structure havevarious problems that should be solved when to make its translucentreflective film. To improve the weather resistance of the translucentreflective film and to reduce the cost thereof are important problemsthat should be solved when to make the optical recording medium havingthe multilayer structure commercially available on the market.

[0022] Weather resistance of the reflective film is important not onlyin the reflective film of the optical recording medium having themultilayer structure but also in the reflective films for use inrewritable optical recording mediums such as a magneto-optical recordingmedium, a phase-change optical recording medium and a dye-system opticalrecording medium in which various material films are laminated asinformation recording layers. When the reflective film is degraded dueto aged deterioration such as oxidation, the deteriorated reflectivefilm changes not only quality of the reproduced signal but alsorecording conditions such as recording sensitivity.

[0023] The AgPdCu thin film or the AgPdTi thin film is inexpensive ascompared with a simple substance of Au from a money standpoint andcannot be separated from the adhesive material or the material of thesubstrate unlike the Si film.

[0024] Recently, a demand for higher recording density or largerrecording capacity is increasing, and laser light with a shortwavelength is used as laser light for use in recording or reproducinginformation, whereby surface recording density can be increased. In thiscase, recording pits should be formed with higher accuracy, and eventhough the amount in which the jitter in the reproduced signal isdeteriorated is small to the extent that it is allowable when thesurface recording density is low, such very small amount of thedeteriorated jitter raises a serious problem as the surface recordingdensity increases.

[0025] Further, as the information recording layer is formed as theinformation recording layer having the two-layer structure as describedabove or the information recording layer is formed as an informationrecording layer having a multilayer structure of more than two layers,the translucent reflective film in each information recording layer atthe entrance end side of inward light is progressively decreasing itsfilm thickness more because reflectance and transmittance of each layerand the like should be selected properly. Therefore, this translucentreflective film needs higher weather resistance.

[0026] Specifically, this translucent reflective film needs high weatherresistance to the extent that reflectance can be prevented from beingchanged and that the jitter in the reproduced signal can be preventedfrom being deteriorated under severe circumstances for a longer time.

[0027] Furthermore, a demand for manufacturing optical recording mediumsmore inexpensively also is increasing more than before.

[0028] An object of the present invention is to provide an opticalrecording medium in which weather resistance of a translucent reflectivefilm and a reflective film comprising information recording layers of anoptical recording medium, in particular, weather resistance of thetranslucent reflective film with a special characteristic such astranslucency can be improved and in which a cost thereof can be reduced.

DISCLOSURE OF INVENTION

[0029] According to the present invention, there is provided an opticalrecording medium including at least an information recording layer and areflective film and in which the reflective film thereof is comprised ofan AgCu alloy thin film containing Cu the content of which is greaterthan 3.0 or equal to [atomic %] and less than or equal to 6.5 [atomic%].

[0030] Moreover, according to the present invention, there is providedan optical recording medium in which at least a first informationrecording layer and a second information recording layer are laminatedto each other and in which the first information recording layer has atranslucent reflective film formed thereon and the second informationrecording layer has a reflective film formed thereon and the translucentreflective film is comprised of an AgCu alloy thin film containing Cuthe content of which is greater than or equal to 3.0 [atomic %] and lessthan 6.5 or equal to [atomic %].

[0031] In this arrangement, information is reproduced from the secondinformation recording layer with irradiation of light that has passedthrough the first information recording layer.

[0032] Moreover, according to the present invention, there is providedan optical recording medium including at least an information recordinglayer and a reflective film and in which the reflective film thereof iscomprised of an AgCu containing alloy thin film containing Cu thecontent of which is greater than or equal to 2.0 [atomic %] and lessthan or equal to 9.0 [atomic %] and this AgCu containing alloy is madeof either an AgCu containing ternary alloy or quaternary alloycontaining one or two chemical elements of Al, Ti, Fe, Ni, Mo, W andwhose total content of the chemical elements is greater than or equal to0.5 [atomic %] and less than or equal to 8.1 [atomic %].

[0033] Further, according to the present invention, there is provided anoptical recording medium in which at least a first information recordinglayer and a second information recording layer are laminated to eachother and in which the first information recording layer has atranslucent reflective film formed thereon, the second informationrecording layer has a reflective film formed thereon, the translucentreflective film thereof is composed of an AgCu containing alloy thinfilm containing Cu the content of which is greater than or equal to 2.0[atomic %] and less than or equal to 9.0 [atomic %] and this AgCucontaining alloy is made of an AgCu containing ternary alloy orquaternary alloy containing one or two chemical elements of Al, Ti, Fe,Ni, Mo, W and whose total content of the chemical elements is greaterthan or equal to 0.5 [atomic %] and less than or equal to 8.1 [atomic%].

[0034] In this arrangement, information is reproduced from the secondinformation recording layer with irradiation of light that has passedthrough the first information recording layer.

[0035] Moreover, according to the present invention, there is providedan optical recording medium including at least an information recordinglayer and a reflective film and in which the reflective film thereof iscomprised of an AgCu containing alloy thin film containing Cu thecontent of which is greater than or equal to 1.5 [atomic %] and lessthan or equal to 9.0 [atomic %] and this AgCu containing alloy is madeof an AgCuPd containing quaternary alloy or quinary alloy containing Pdthe content of which is greater than or equal to 0.1 [atomic %] and lessthan or equal to 2.0 [atomic %] and which contains one or two chemicalelements of Al, Ti, Fe, Ni, Mo, W and whose total content of thechemical elements is greater than or equal to 0.5 [atomic %] and lessthan or equal to 8.1 [atomic %].

[0036] Further, according to the present invention, there is provided anoptical recording medium in which at least a first information recordinglayer and a second information recording layer are laminated to eachother and in which the first information recording layer has atranslucent reflective film formed thereon, the second informationrecording layer has a reflective film formed thereon, the translucentreflective film is comprised of an AgCu containing alloy thin filmcontaining Cu the content of which is greater than 1.5 or equal to[atomic %] and less than 9.0 or equal to [atomic %] and this AgCu alloyis made of either an AgCuPd containing quaternary alloy or quinary alloycontaining Pd the content of which is greater than or equal to 0.1[atomic %] and less than or equal to 2.0 [atomic %] and which containsone or two chemical elements of Al, Ti, Fe, Ni, Mo, W and whose totalcontent of the chemical elements is greater than or equal to 0.5 [atomic%] and less than or equal to 8.1 [atomic %].

[0037] In this arrangement, information is reproduced from the secondinformation recording layer with irradiation of light that has passedthrough the first information recording layer.

[0038] Then, in the above-mentioned optical recording medium includingat least the first and second information recording layers, the firstinformation recording layer is formed on a first substrate, the secondinformation recording layer is formed on a second substrate, the firstand second substrates can be laminated to each other in such a mannerthat information recording layers thereof may be facing to each otherand information is reproduced from the first and second informationrecording layers with irradiation of light from the first substrateside.

[0039] As described above, according to the arrangement of the presentinvention, in the optical recording medium including the reflectivefilm, the reflective film thereof is composed of an AgCu alloy, an AgCucontaining alloy and further an AgCuPd containing alloy thin film and inthe optical recording medium including the reflective film and thetranslucent reflective film, at least the translucent reflective film iscomposed of an AgCu alloy, an AgCu containing alloy and further anAgCuPd containing alloy thin film. Therefore, it became possible toobtain an optical recording medium which can be made excellent inweather resistance and which can be made inexpensive.

[0040] Further, according to the present invention, in the AgCucontaining alloy and AgCuPd containing alloy comprising the reflectivefilm or the translucent reflective film or the reflective film and thetranslucent reflective film, since added chemical elements suitable forcomprising these alloys are specified and their containing ratios arespecified, the reflective film or the translucent reflective film or thereflective film and the translucent reflective film can be improved inweather resistance. Even after the optical recording medium has beenstored for a long time under the conditions of high temperature and highhumidity, for example, optical characteristics such as reflectance andtransmittance required by the information recording layer of the opticalrecording medium or recording density can be effectively avoided frombeing changed.

[0041] According to the arrangement of the present invention, as willbecome clear from descriptions which will be made later on, it isintended to obtain an optical recording medium which can exhibit higherweather resistance and which can be made inexpensive, accordingly, whichcan be manufactured inexpensively.

BRIEF DESCRIPTION OF DRAWINGS

[0042]FIG. 1 is a schematic cross-sectional view showing an example ofan optical recording medium including two-layer information recordinglayers according to the present invention.

[0043]FIG. 2 is a schematic cross-sectional view showing another exampleof an optical recording medium according to the present invention.

[0044]FIG. 3 is a schematic cross-sectional view showing amagneto-optical recording layer portion of a magneto-optical recordingmedium in an enlarged-scale.

[0045]FIG. 4 is a schematic cross-sectional view showing an example ofan optical recording medium according to the prior art.

[0046]FIG. 5 is a diagram showing a relationship between recording powerand a CNR obtained before and after the storage tests.

[0047]FIG. 6 is a table (table 1-1) listing or enumerating arrangementsof samples having various optical disc structures.

[0048]FIG. 7 is a table (table 1-2 enumerating characteristics of therespective samples shown in FIG. 6.

[0049]FIG. 8 is a table (table 2-1) enumerating arrangements of sampleshaving various optical disc structures.

[0050]FIG. 9 is a table (2-2) enumerating characteristics of therespective samples shown in FIG. 8.

[0051]FIG. 10 is a table (3-1) enumerating arrangements of sampleshaving various optical disc structures. FIG. 11 is a table (table 3-2enumerating characteristics of the respective samples shown in FIG. 10.

[0052]FIG. 12 is a table (table 4-1) enumerating arrangements of sampleshaving various optical disc structures.

[0053]FIG. 13 is a table (table 4-2) enumerating characteristics of therespective samples shown in FIG. 12.

[0054]FIG. 14 is a table (table 5-1) enumerating arrangements of sampleshaving various optical disc structures.

[0055]FIG. 15 is a table (table 5-2) enumerating characteristics of therespective samples shown in FIG. 14.

BEST MODE FOR CARRYING OUT THE INVENTION

[0056] An optical recording medium according to the embodiments of thepresent invention will be described below with reference to thedrawings. It is needless to say that the optical recording mediumsaccording to the present invention are not limited to the followingexamples.

[0057]FIG. 1 is a schematic cross-sectional view showing an opticalrecording medium 10 according to the present invention.

[0058] In the optical recording medium 10, first and second substrates 1and 2 are laminated to each other through a transparent adhesive agentlayer 3 in such a manner that information recording layers 21 and 22formed on these substrates 1 and 2 maybe facing to each other. Thisoptical recording medium is manufactured in accordance with a DVD(Digital Versatile Disc) format having a two-layer structure in whichthe first and second information recording layers 21 and 22 arelaminated to each other.

[0059] The first and second information recording layers 21 and 22 areindented to have first and second very small indentations 11 and 12corresponding to recording information. The first very smallindentations 11 have a translucent reflective film 13 deposited thereonto pass or reflect the irradiated light for recording and/or reproducingthe optical recording medium. The second very small indentations 12 havea reflective film 14 deposited thereon to reflect similar irradiatedlight.

[0060] The first substrate 1 can be molded by injection molding of aplastic material such as polycarbonate that can pass the above-mentionedirradiated light. In this case, the first very small indentations 11also can be formed on the first information recording layer 21 on thefirst substrate 1 at the same time the first substrate 1 is molded byinjection molding.

[0061] The second substrate 2 can be similarly molded by injectionmolding of a plastic material such as polycarbonate regardless of thekind of plastic materials, such as a transparent plastic material or anopaque plastic material. The second very small indentations 12 can beformed on the second information recording layer 22 at the same time thesecond substrate 2 is molded.

[0062] A translucent reflective film 13 is deposited on the first verysmall indentations 11 of the first information recording layer 21.

[0063] This translucent reflective film 13 is made of an AgCu alloy thinfilm or an AgCu containing alloy thin film having a film thicknessranging from 10 [nm] to 15 [nm] such that it may reflect and pass partof the above-mentioned irradiated light, e.g., laser beams.

[0064] AgCu alloy containing Cu the content of which is greater than orequal to 3.0 [atomic %] and less than or equal to 6.5 [atomic %] can beapplied as the AgCu alloy comprising the translucent reflective film 13.

[0065] The translucent reflective film 13 may be made of an AgCucontaining ternary alloy or quaternary alloy which is an AgCu alloycontaining Cu the content of which is greater than or equal to 2.0[atomic %] and less than or equal to 9.0 [atomic %] and which containsone or two chemical elements of Al, Ti, Fe, Ni, Mo, W and whose totalcontent of the chemical elements is greater than or equal to 0.5 [atomic%] and less than or equal to 8.1 [atomic %].

[0066] Alternatively, the translucent reflective film 13 may be made ofan AgCuPd containing quaternary alloy or quinary alloy which is an AgCucontaining alloy containing Cu the content of which is greater than orequal to 1.5 [atomic %] and less than or equal to 9.0 [atomic %] andwhich contains Pd the content of which is greater than or equal to 0.1[atomic %] and less than or equal to 2.0 [atomic %] and which containsat least one or more than two chemical elements of Al, Ti, Fe, Ni, Mo, Wand in which the total content of these chemical elements is greaterthan or equal to 0.5 [atomic %] and less than or equal to 8.1 [atomic%].

[0067] In the second information recording layer 22, a reflective film14 is deposited on the above-mentioned second very small indentations12.

[0068] This reflective film 14 may be made of a metal material having ahigh reflectance, e.g., Au, an alloy whose principal component is Au,e.g., Ag or an alloy whose principal component is Ag, or Pt or an alloywhose principal component is Pt or Cu or an alloy whose principalcomponent is Cu and the like.

[0069] Moreover, in order to reduce the costs, the reflective film 14may be made of an Al alloy in which other metal material such as Si, Tior Cr is added to Al.

[0070] However, in order to improve weather resistance of the reflectivefilm and in order to reduce the cost of the reflective film, thereflective film 14 may be made of the above-mentioned AgCu alloy, AgCucontaining ternary or quaternary alloy and AgCuPd containing quaternaryor quinary alloy having similar materials and compositions to those ofthe above-mentioned translucent reflective film, and the film thicknessof the reflective film can be selected in a range of from 35 [nm] to 60[nm], for example.

[0071] The translucent reflective film 13 and the reflective film 14 canboth be deposited by conventional sputtering, in general, magnetronsputtering.

[0072] A set of optical heads should be used to reproduce signals fromthe first and second information recording layers 21 and 22 or to recordsignals on the first and second information recording layers of theoptical recording medium 10 with irradiation of laser beams from thesame side of the optical recording medium 10, e.g., from the firstsubstrate 1 side in the arrangement shown in FIG. 1 so that a driveapparatus therefor can be simplified, the optical heads can access theseinformation recording layers 21 and 22 in a short time and cancontinuously record or reproduce these information recording layers.

[0073] When the optical head irradiates laser beams on the first andsecond information recording layers from the same side of the opticalrecording medium 10 to reproduce or record the first and secondinformation recording layers, the same optical head focuses a laser beamL on the first information recording layer 21 to reproduce or record thefirst information recording layer as shown by a solid line in FIG. 1 andthe same optical head focuses a laser beam L on the second informationrecording layer 22 to reproduce or record the second informationrecording layer as shown by a dotted line in FIG. 1.

[0074] Next, a case in which the optical recording medium according tothe present invention is applied to a magneto-optical recording mediumwill be described.

[0075]FIG. 2 is a schematic cross-sectional view showing an example of amagneto-optical recording medium 100.

[0076] The magneto-optical recording medium 100 comprises a substrate101 made of a resin having transmittance such as polycarbonate, verysmall indentations 102 such as pregrooves, formed on the substrate atthe same time the substrate is formed by injection molding, aninformation layer 105 formed of a magneto-optical recording layer 104 onthe very small indentations 102 and a protective layer 106 formed on theinformation layer 105.

[0077]FIG. 3 is a schematic cross-sectional view showing a laminationlayer structure of the magneto-optical recording layer 104 of themagneto-optical recording medium 100 shown in FIG. 2.

[0078] The magneto-optical recording layer 104 may have a laminatinglayer arrangement shown in FIG. 3.

[0079] This magneto-optical recording layer 104 comprises the substrate101, for example, on which a first dielectric layer 41 made of SiN_(x),for example, and whose film thickness is approximately 40 [nm], arecording layer 42 made of TbFeCo, for example, and whose film thicknessis approximately 15 [nm], a translucent heat adjustment film 43 made ofan AgCu containing alloy, which will be described later on, and whosefilm thickness is approximately 10 [nm], a second dielectric layer 44made of SiN_(x), for example, and whose film thickness is approximately20 [nm] and a reflective film 45 made of an AgCu containing alloy, whichwill be described later on, and whose film thickness is approximately 40[nm] are laminated, in that order.

[0080] The heat adjustment film 43 and the reflective film 45 shown inFIG. 3 can be made of an AgCu alloy thin film or an AgCu containingalloy thin film similarly to the aforementioned translucent reflectivefilm 13 and the reflective film 14.

[0081] AgCu alloy containing Cu the content of which is greater than orequal to 3.0 [atomic %] and less than or equal to 6.5 [atomic %] can beapplied to the AgCu alloy.

[0082] Alternatively, the translucent reflective film and the reflectivefilm can be made of an AgCu containing ternary alloy or quaternary alloywhich is an AgCu containing alloy containing Cu the content of which isgreater than or equal to 2.0 [atomic %] and less than or equal to 9.0[atomic %] and which contains one or two chemical elements of Al, Ti,Fe, Ni, Mo, W and in which the total content of the chemical elements isgreater than or equal to 0.5 [atomic %] and less than or equal to 8.1[atomic %].

[0083] Alternatively, the translucent reflective film and the reflectivefilm can be made of an AgCuPd containing quaternary or quinary alloywhich is an AgCu containing alloy containing Cu the content of which isgreater than or equal to 1.5 [atomic %] and less than or equal to 9.0[atomic %] and which contains Pd the content of which is greater than orequal to 0.1 [atomic %] and less than or equal to 2.0 [atomic %] andwhich contains at least one or more than two chemical elements of Al,Ti, Fe, Ni, Mo, W and in which the total contents of the chemicalelements is greater than or equal to 0.5 [atomic %] and less than orequal to 8.1 [atomic %].

[0084] The protective layer 106 may be made of a conventionalultraviolet-curing resin that can be cured by spin-coating.

[0085] Information is recorded on or reproduced from the magneto-opticalrecording medium 100 shown in FIG. 2 by laser beams irradiated on themagneto-optical recording medium from the side of the substrate 101.

[0086] Specifically, the optical head focuses a laser beam L on theinformation layer 105 as shown by a solid line in FIG. 2 to recordinformation on the magneto-optical recording medium or to reproduceinformation from the magneto-optical recording medium.

[0087] Next, in order to understand the characteristics of the opticalrecording medium according to the present invention, we had manufacturedsamples having respective disc structures including the embodiments ofthe optical recording medium according to the present invention,whereafter we had measured respective characteristics, i.e., weatherresistances.

[0088] In these samples, the reason that we had manufactured samples ofdiscs of structures in which an information recording layer is formed ononly a one substrate (this sample of disc will hereinafter be referredto as a “single plate”) whereafter we have measured characteristics ofthese samples will be described below. That is, when the thickness ofthe substrate, for example, is selected to be 0.6 [nm], since entirerigidity of such substrate is inferior to that of the structure in whichfirst and second information recording layers are sandwiched between twosubstrates, the substrate is warped considerably after it has beenstored by the storage test, and adhesion between the alloy thin filmcomprising the translucent reflective film, for example, and thesubstrate is lowered, thereby causing the alloy thin film and thesubstrate to be easily separated from each other. As a consequence, itbecomes able to estimate weather resistance very strictly.

[0089] Moreover, in the sample concerning the optical disc of thestructure in which two substrates corresponding to the first and secondsubstrates 1 and 2 corresponding to the first and second informationrecording layers 21 and 22 are laminated to each other, the alloy thinfilm corresponding to the reflective film 14 is made of an AlTi materialof an ordinary alloy thin film unlike the alloy thin film in thetranslucent reflective film, because deterioration of such sample of theabove optical disc in which alloy thin films of different nature arelaminated to each other is unavoidably accelerated under circumstanceswith high humidity and therefore we can estimate weather resistance ofsuch sample more strictly. Specifically, in the samples of thisstructure in which two substrates are laminated to each other, when thetranslucent reflective film and the reflective film are both made of anAgCu alloy, an AgCu containing alloy or an AgCuPd containing alloy,these samples can exhibit more excellent weather resistance.

[0090] That is, we have studied characteristics of the materials of thetranslucent reflective films more strictly based upon the respectivesamples.

[0091] [Sample 1]:

[0092] First, a 0.6 [nm]-thick substrate was molded by injection moldingof polycarbonate.

[0093] At the same time the substrate was molded, very smallindentations, i.e., pit data rows modulated by using an EFM code inwhich a track pitch was 0.74 [μm], a depth of pit was 110 [nm] and ashortest pit length was 0.44 [μm] were formed on one major surface ofthis substrate.

[0094] A translucent reflective film made of Ag_(100−x)Cu_(x) (x isatomic %) where x=3.0 and whose film thickness ranges from 10 [nm] to 15[nm] was deposited on the substrate in which the pit data rows areformed by magnetron sputtering, thereby resulting in the firstinformation recording layer 21 being formed.

[0095] Next, a protective layer was formed over the whole surface of theAgCu alloy translucent reflective film by spin-coating and curing aultraviolet-curing resin.

[0096] [Sample 2]:

[0097] In a similar arrangement to that of the sample 1, a translucentreflective film had a composition in which x=6.5.

[0098] [Sample 3]

Inventive Example 1

[0099] This sample had a structure corresponding to that shown in FIG. 1and in which the first and second substrates 1 and 2 including the firstand second information recording layers 21 and 22 are laminated to eachother.

[0100] In this case, the first substrate 1 having the arrangementsimilar to that of the substrate of the sample 1 was prepared. An AgCualloy thin film having a composition of Ag_(100−x)Cu_(x) where x=3.0 wasdeposited on the first substrate by magnetron sputtering to deposit thetranslucent reflective film 13 having the film thickness ranging from 10to 15 [nm], thereby resulting in the first information recording layer21 being formed.

[0101] On the other hand, there was manufactured the second substrate 2having the arrangement similar to that of the first substrate 1. On thesecond substrate 2, there was deposited the reflective film 14 made ofan AlTi alloy thin film having a film thickness 50 [nm] by magnetronsputtering, thereby resulting in the second information recording layer22 being formed.

[0102] Then, the first and second substrates 1 and 2 were laminated toeach other by using a ultraviolet-curing resin as a transparent adhesiveagent in such a manner that their information recording layers 21 and 22may be facing to each other, thereby resulting in an optical disc havinga laminated structure being manufactured.

[0103] In this connection, the film thickness of the AgCu containingalloy film deposited on the first substrate 1 is selected in such afashion that, when an Al alloy film having a film thickness ranging from35 to 60 [nm] or an Ag alloy film having a film thickness ranging from30 to 60 [nm] is formed as the reflective film 14 on the secondsubstrate 2 by laser beams having a wavelength of 660 [nm], reflectanceof the first information recording layer 21 and that of the secondinformation recording layer 22 may become nearly equal to each other.

[0104] [Sample 4]

Comparative Example 1

[0105] Although this sample had an arrangement similar to that of thesample 1 and was manufactured by a similar method, its alloy thin filmhas an alloy atomic composition expressed as Ag_(100−x)Cu_(x) wherex=2.0.

[0106] [Sample 5]

Comparative Example 2

[0107] Although this sample had an arrangement similar to that of thesample 1 and was manufactured by a similar method, its alloy thin filmhas an alloy atomic composition expressed as Ag_(100−x)Cu_(x) wherex=7.0.

[0108] [Sample 6]

Comparative Example 3

[0109] Although this sample had an arrangement similar to that of thesample 1 and was manufactured by a similar method, its alloy thin filmhas an alloy atomic composition expressed as Ag_(100−x)Cu_(x) wherex=9.0

[0110] [Sample 7]

Comparative Example 4

[0111] Although this sample had an arrangement similar to that of thesample 1 and was manufactured by a similar method, instead of its Ag₁₀₀_(x)Cu_(x) alloy thin film, an Si film having a film thickness rangingfrom 10 to 15 [nm] was deposited on the first substrate 1 by magnetronsputtering, thereby resulting in the first information recording layer21 being formed.

[0112] Next, similarly to the first substrate 1, the reflective film 14made of an AlTi alloy thin film having a film thickness of 50 [nm] wasdeposited on the second substrate 2 by magnetron sputtering, therebyresulting in the second information recording layer 22 being formed.

[0113] Similarly to the sample 3, these first and second substrates 1and 2 were laminated to each other by using the ultraviolet-curing resinas the transparent adhesive agent in such a manner that theirinformation recording layers 21 and 22 may be facing to each other,whereby the optical disc of the laminated structure was manufactured.

[0114] [Sample 8]

Comparative Example 5

[0115] Although this sample had the arrangement similar to that of thesample 1 and was manufactured by a similar method, an Ag film having afilm thickness ranging from 10 to 15 [nm] was deposited as itstranslucent reflective film.

[0116] The storage test under circumstances with high temperature andhigh humidity was effected on the above-mentioned respective samples 1to 8 and reflectances [%] and jitter [%] of the respective informationrecording layers 21, 22 were measured, whereby ratios [%] at whichreflectances of the information recording layers are changed before andafter the storage test were calculated.

[0117] In the storage test under circumstances with high temperature andhigh humidity, the optical discs of the respective samples were leftwithin a storage bath with RH circumstances having a temperature of 85°C. and a humidity of 90% for 100 hours.

[0118] Jitter values were measured by an optical pickup having asemiconductor laser having a wavelength of 660 [nm] and an objectivelens having a numerical aperture of 0.60.

[0119] Tables 1-1 and 1-2 of FIGS. 6 and 7 show compositions (atomic %)of materials of deposited translucent reflecting films, optical discstructures, measured results of reflectances [%] and jitters [%] of therespective information recording layers 21, 22 obtained before and afterthe storage test and amounts with which reflectances of the informationrecording layers were changed before and after storage test with respectto the respective samples 1 to 8.

[0120] In the tables, R₁ [%] shows reflectances of the first informationrecording layers 21 of the respective samples (optical discs) of thesingle plate structure and the laminating structures obtained at theinitial stage, i.e., reflectances obtained before the storage test, andR₃ [%] shows reflectances obtained after the storage tests of thesesamples.

[0121] In the tables, R₂ [%] shows reflectances of the secondinformation recording layers 22 of the samples (optical discs) of thelaminating structures obtained at the initial stage, and R₄ [%] showsreflectances of the second information recording layers of these samplesobtained after the storage test.

[0122] Further, the amount with which the reflectance is changed beforeand after the storage test is shown by |R₁−R₃| [%].

[0123] It is to be understood that, with respect to the samples 1 to 3in which Ag_(100−x)Cu_(x) (3≦x≦6.5) thin films were deposited on theinformation recording layers of the optical discs of the single platestructures and the first information recording layers 21 of the opticaldiscs of the laminating structures as shown on the tables 1 (FIGS. 6 and7), the changes of the reflectances obtained before and after thestorage test could be decreased to less than 1.0 [%], the changes of thejitters obtained before and after the storage test could be suppressedto be less than 1 [%] so that the optical characteristics with excellentweather resistance could be obtained.

[0124] In the samples 4 to 7 (comparative examples 1 to 4) the amountsin which the reflectances were changed before and after the storage testhad exceeded 1.0 [%]. In the sample 8 (comparative example 5), therearose a problem that the jitter value obtained after the storage testwere increased so that a signal could not be reproduced with stability.

[0125] Next, there were manufactured samples 9 to 39 in which either anAgCu (Al, Ti, Fe, Ni, Mo, W) ternary alloy or quaternary alloycontaining Cu the content of which is greater than or equal to 2.0[atomic %] and less than or equal to 9.0 [atomic %] and which containsone or two chemical elements of Al, Ti, Fe, Ni, Mo, W and in which thetotal content of the chemical elements is greater than or equal to 0.5[atomic %] and less than or equal to 8.1 [atomic %] was deposited on theinformation recording layers.

[0126] [Sample 9] to [Sample 31]:

[0127] These samples were optical discs of single plates havingarrangements similar to that of the sample 1 and were manufactured by asimilar method. In these samples, instead of the AgCu alloy filmdeposited on the substrate 1, the translucent reflective film 13 wasmade of an Ag_(100−x−y)Cu_(x)A_(y) (A is one or two chemical elements ofAl, Ti, Fe, Ni, Mo, W and x, y represent atomic % respectively) thinfilm having a film thickness ranging from 10 to 15 [nm] where 2≦x≦9.0and 0.5≦y≦8.1.

[0128] [Sample 32] (Inventive Example 2) to [Sample 38] (InventiveExample 8):

[0129] These samples of the laminating structures of the first andsecond substrates 1 and 2 having the first and second informationrecording layers 21 and 22 shown in FIG. 1 had arrangements similar tothat of the sample 3 and were manufactured by the similar method. Inthese samples 32 to 38, the translucent reflective film 13 on the firstsubstrate 1 was made of an Ag_(100−x−y)Cu_(x)A_(y) (A is one or twochemical elements of Al, Ti, Fe, Ni, Mo, W and x, y represent atomic %respectively) alloy thin film having a film thickness ranging from 10 to15 [nm] where 2≦x≦9 and 0.5≦y≦8.1.

[0130] [Sample 39]

Comparative Example 6

[0131] This sample had a similar arrangement to that of the sample landwas manufactured by a similar method. In this sample 39, the translucentreflective film 13 there of has an alloy atomic composition expressed asAg_(100−x−y)Cu_(x)A_(y) (A was Al and Ti) where x=5.4 and y=8.5.

[0132] Other conditions were similar to those of [sample 1] and thesample of the optical disc of the single plate structure wasmanufactured.

[0133] With respect to the above-mentioned samples 9 to 39, thecompositions (atomic %) of the materials forming their translucentreflecting films and the optical disc structures are shown on tables 2-1and 3-1 of FIGS. 8 and 10. The similar storage test under circumstanceswith high temperature and high humidity was effected on these samplesand test results are shown on tables 2-2 and 3-2 of FIGS. 9 and 11.

[0134] In the samples 9 to 38 having the information recording layers ofthe optical disc of the single plate structures and the firstinformation recording layers 21 of the optical disc of the laminatingstructures in which alloy atomic compositions were expressed asAg_(100−x−y)Cu_(x)A_(y) (A is at least one of Al, Ti, Fe, Ni, Mo, W) andin which 2≦x≦9 and 0.5≦y≦8.1, the amounts in which the reflectances werechanged before and after the storage test could be decreased to be lessthan 1.0 [%] and the amounts in which the jitters were changed beforeand after the storage test could be suppressed to be less than 1 [%]. Inparticular, there could be obtained optical characteristics withexcellent weather resistance.

[0135] On the other hand, in the sample 39 (comparative example 6), theamounts in which the reflectances were changed before and after thestorage test exceeded 1.0 [%] and the weather resistance wasdeteriorated.

[0136] Next, there are shown samples (optical discs) in whichtranslucent reflective films made of AgCuPd containing quaternary alloyor quinary alloy containing Cu the content of which is greater than 1.5[atomic %] and less than 9.0 [atomic %] and which contains one or twochemical elements of Al, Ti, Fe, Ni, Mo, W and in which the totalcontent of the chemical elements is greater than or equal to 0.5 [atomic%] and less than or equal to 8.1 [atomic %] and which contains Pd thecontent of which is greater than or equal to 0.1 [atomic %] and lessthan or equal to 2.0 [atomic %] were deposited on the informationrecording layers.

[0137] [Sample 40] to [Sample 60]:

[0138] Although these samples had the single plate structures havingsimilar structures to that of the sample 1 and were manufactured by thesimilar method, their translucent reflective films 13 had alloy atomiccompositions expressed as Ag_(100−x−y−z)Pd_(z)Cu_(x)A_(y) (A is one ofAl, Ti, Fe, Ni, Mo and W and x, y, z represent atomic % respectively)where 1.5≦x≦9.0, 0.5≦y≦8.1 and 0.1≦z≦2.0.

[0139] [Sample 61] (Inventive Example 9) to [Sample 65] (InventiveExample 13):

[0140] Although these samples had similar structures to that of thesample 3 (inventive example 1) and were manufactured by the similarmethod, their translucent reflective films 13 had alloy atomiccompositions expressed as Ag_(100−x−y−z)Pd_(x)Cu_(x)A_(y) (A is one ofAl, Ti, Fe, Ni, Mo and W and x, y, z represent atomic % respectively)where 1.5≦x≦9.0, 0.5≦y≦8.1 and 0.1≦z≦2.0.

[0141] [Sample 66]

Comparative Example 7

[0142] Although this sample had a similar structure to that of thesample 1 and was manufactured by the similar method, its translucentreflective film 13 had an alloy atomic composition expressed asAg_(100−x−y−z)Pd_(z)Cu_(x)A_(y) (A is Al) where x=4.0, y=9.0 and z=0.9.

[0143] [Sample 67]

Comparative Example 8

[0144] Although this sample had a similar structure to that of thesample 1 and was manufactured by the similar method, its translucentreflective film 13 had an alloy atomic composition expressed asAg_(100−x−y−z)Pd_(z)Cu_(x)A_(y) where x=1.5, y=0.0 and z=0.9.

[0145] [Sample 68]

Comparative Example 9

[0146] Although this sample had a similar structure to that of thesample 1 and was manufactured by the similar method, its translucentreflective film 13 had an alloy atomic composition expressed asAg_(100−x−y−z)Pd_(z)Cu_(x)A_(y) where x=1.5, y=0.0 and z=0.9.

[0147] [Sample 69]

Comparative Example 10

[0148] Although this sample had a similar structure to that of thesample 3 and was manufactured by the similar method, its translucentreflective film 13 had an alloy atomic composition expressed asAg_(100−x−y−z)Pd_(z)Cu_(x)A_(y) where x=1.5, y=0.0 and z=0.9.

[0149] [Sample 70]

Comparative Example 11

[0150] Although this sample had a similar structure to that of thesample 3 and was manufactured by the similar method, its translucentreflective film 13 had an alloy atomic composition expressed asAg_(100−x−y−z)Pd_(z)Cu_(x)A_(y) where x=4.0, y=0.0 and z=0.9.

[0151] With respect to the optical discs of the above-mentioned samples57 to 70, tables 5-1 and 5-2 of FIGS. 14 and 15 show compositions(atomic %) of materials forming their translucent reflective films,optical disc structures and test results obtained after the similarstorage tests effected under circumstances with high temperature andhigh humidity.

[0152] As shown on the tables 5-1 and 5-2 of FIGS. 14 and 15, in thesamples 40 to 65 in which the first information recording layers 21 ofthe single plate structures and the laminating structures have alloyatomic compositions expressed as Ag_(100−x−y−z)Pd_(z)Cu_(x)A_(y) where Ais one or two kinds of chemical elements of Al, Ti, Fe, Ni, Mo, W and1.5≦x≦9.0, 0.5≦y≦8.1 and 0.1≦z≦2.0, the amount with which thereflectances were changed before and after the storage test could bedecreased to be less than 1.0 [%], the amount in which the jitters werechanged before and after the storage test could be suppressed to be lessthan 1 [%], and in particular, optical characteristics with excellentweather resistance could be obtained.

[0153] In the sample 66 (comparative example 7), the jitter valueobtained after the storage test was increased so that a signal could notbe reproduced with high stability.

[0154] In the optical discs shown in the sample 67 (comparative example8) to the sample 70 (comparative example 11), the amounts in whichreflectances are changed before and after the storage test exceeded 1.0[%] and weather resistance was deteriorated.

[0155] As is clear from the above description, according to the presentinvention, the AgCu alloy thin film or the AgCu containing alloy thinfilm is applied to the information recording layer, the composition ofthe above alloy thin film is specified, the chemical element of theabove composition is selected and the content of such chemical elementis specified, whereby the weather resistance of the informationrecording layer can be improved, the amounts in which the opticalcharacteristics such as the reflectance or the transmittance required bythe information recording layer of the optical recording medium arechanged after the optical recording medium has been stored for a longtime under conditions with high temperature and high humidity can besuppressed to be low and the deterioration of the jitter can be avoidedeffectively. Moreover, the cost of the optical recording mediumaccording to the present invention can be reduced as compared with thatof the prior-art optical recording medium.

[0156] While the optical discs of ROM (Read Only Memory) type have beenillustrated so far in the above-mentioned respective samples, thepresent invention is not limited to those examples and can be alsoapplied to rewritable optical discs, such as a magneto-optical recordingdisc and a phase-change recording disc. When the AgCu alloy thin filmcomprising the information recording layer of the present invention isapplied to the reflective film or the heat structure film, the weatherresistance can be improved and the amount in which the recording densityis changed due to aged deterioration caused after the optical disc hadbeen stored for a long time can be decreased. As a result, stablerecording becomes possible, and the jitter can be effectively avoidedfrom being deteriorated.

[0157] For example, the present invention was applied to themagneto-optical recording medium 100 shown in FIG. 3 and change ofrecording sensitivity was measured.

[0158] The magneto-optical recording medium 100 comprises the substrate101 on which there are laminated the first dielectric layer 41 made ofSiN_(x) having a film thickness of 40 [nm], the recording layer 42 madeof TbFeCo having a film thickness of 15 [nm], the heat adjustment film43 formed of the translucent reflective film made of AgCu containingalloy having a film thickness of approximately 10 [nm], the seconddielectric layer 44 made of SiN_(x) having a film thickness ofapproximately 20 [nm] and the reflective film 45 made of AgCu containingalloy having a film thickness of approximately 40 [nm], in that order.

[0159] We had manufactured magneto-optical disk samples in which theheat adjustment film 43 and the reflective film 45 were formed ofAgPd_(0.9)Cu_(1.5) alloy thin films and magneto-optical disks formed ofAgCu_(0.9)Ti_(1.7) alloy thin films.

[0160] In this case, a mark length of 0.3 [μm] was recorded on themagneto-optical recording layer 104 deposited on the substrate 101 inwhich recording guide grooves, formed of so-called lands and grooves,having a track pitch of 0.80 [μm] and a groove depth of 30 [nm] wereformed under respective conditions in which a wavelength of laser lightwas selected to be 405 [nm], a numerical aperture of an objective lenswas selected to be 0.60 and a linear velocity was selected to be 4.6[m/s] by a method called magnetic field modulation recording, and we hadmeasured relationships between recording power and CNRs of reproducedsignals obtained before and after the above-mentioned storage test.

[0161]FIG. 5 shows measured results. In FIG. 5, solid squares and opensquares show measured results obtained before and after the storagetests had been effected on the magneto-optical disks in whichAgPd_(0.9)Cu_(1.5) alloy thin films were deposited, and solid circlesand open circles show measured results obtained before and after thestorage tests had been effected on the magneto-optical disks in whichAgCu_(0.9)Ti_(1.7) alloy thin films were deposited.

[0162] As shown in FIG. 5, in the magneto-optical disks in which theAgPd_(0.9)Cu_(1.5) alloy thin films were deposited, recording powerobtained after the storage test under high temperature and high humidityconditions was shifted in the increasing direction of approximately 10%.That is, after the magneto-optical disks had been left under hightemperature and high humidity conditions, atoms in the deposited thinfilm are caused to move to increase density of the thin film with theresult that thermal conductivity increases and energy loss increases.

[0163] On the other hand, in the magneto-optical disk in which theAgCu_(0.9)Ti_(1.7) alloy thin film in the magneto-optical disk accordingto the example of the optical recording medium of the present inventionwas deposited, after the storage test under high temperature and highhumidity conditions, it is to be understood that recording power is notincreased, energy loss is small and that the film characteristic isextremely excellent in weather resistance.

[0164] In general, thermal conductivity of metal material may increasein the metal material having higher reflectance, and conversely, thermalconductivity of metal material may decrease as its reflectance maydecrease. Moreover, recording density may decrease as thermalconductivity of metal material may increase. Stated otherwise, recordingdensity may increase as thermal conductivity may decrease.

[0165] It is possible to estimate changes of recording sensitivity bymeasuring the amounts in which reflectances of the reflective film werechanged before and after the storage test. Therefore, from therespective inventive examples shown on [table 1] to [table 5], it ispossible to estimate the changes of recording sensitivity in variouscompositions.

[0166] Although the present invention is characterized in that AgCualloy or AgCuPd alloy contain more than one kind of any one of Al, Ti,Fe, Ni, Mo, W, it is to be expected that the above-mentioned alloy cancontain V, Cr, Mn, Co, Y, Zr, Nb, Ru, Ta which are transition metalshaving similar chemical nature in addition to such added chemicalelements with similar effects to those of the present invention beingachieved.

[0167] The optical recording medium according to the present inventionis not limited to the optical recording mediums having informationrecording layers of single layer and two layers and the presentinvention can similarly be applied to optical recording mediums havingmultilayer structures in which information recording layers of more thanthree layers, for example, are laminated to one another.

[0168] Further, while the substrate comprising the optical recordingmedium is formed by injection molding in the above-mentioned examples,the present invention is not limited to the above-mentioned examples andcan also be applied to the case of an optical recording medium in whichvery small indentations are formed on a plate having a smooth surface by2P (Photo polimerization).

[0169] Furthermore, while the examples of the disc-like and disk-shapedoptical recording mediums have been described so far in theabove-mentioned examples, the present invention is not limited to thoseexamples and can be applied to optical recording mediums of variousshapes such as a card-like optical recording medium and a sheet-likeoptical recording medium as well.

DESCRIPTION OF REFERENCE NUMERALS

[0170]1 first substrate

[0171]2 second substrate

[0172]3 transparent adhesive layer

[0173]10 optical recording medium

[0174]11 first very small indentations

[0175]12 second very small indentations

[0176]13 translucent reflective film

[0177]14 reflective film

[0178]21 first information recording layer

[0179]22 second information recording layer

[0180]41 first dielectric layer

[0181]42 recording layer

[0182]43 heat adjustment film

[0183]44 second dielectric layer

[0184]45 reflective film

[0185]100 optical recording medium

[0186]101 substrate

[0187]102 very small indentations

[0188]104 magneto-optical recording layer

[0189]105 information layer

[0190]106 protective film

[0191]200 optical recording medium

[0192]201 first substrate

[0193]202 second substrate

[0194]203 transparent adhesive layer

[0195]211 first very small indentations

[0196]222 second very small indentations

[0197]223 translucent reflective film

[0198]224 reflective film

[0199]231 first information recording layer

[0200]232 second information recording layer

1. (canceled)
 2. (amended) In an optical recording medium in which atleast a first information recording layer and a second informationrecording layer are laminated to each other, an optical recording mediumcharacterized in that said first information recording layer has atranslucent reflective film formed thereon, said second informationrecording layer has a reflective film formed thereon, said translucentreflective film has a thickness greater than 10 nm and less than 15 nmand is made of an AgCu alloy containing Cu the content of which isgreater than or equal to 3.0 [atomic %] and less than or equal to 6.5[atomic %] and information is reproduced from said second informationrecording layer with irradiation of light that has passed through saidfirst information recording layer.
 3. (amended) In an optical recordingmedium including at least an information recording layer and areflective film, an optical recording medium characterized in that saidreflective film is made of an AgCu containing alloy containing Cu thecontent of which is greater than or equal to 2.0 [atomic %] and lessthan or equal to 9.0 [atomic %] and said AgCu containing alloy is madeof an AgCu containing either of ternary alloy and quaternary alloycontaining one or two chemical elements of Fe, Ni, Mo, W and whose totalcontent of said chemical elements is greater than or equal to 0.5[atomic %] and less than or equal to 8.1 [atomic %].
 4. (amended) In anoptical recording medium in which at least a first information recordinglayer and a second information recording layer are laminated to eachother, an optical recording medium characterized in that said firstinformation recording layer has a translucent reflective film formedthereon, said second information recording layer has a reflective filmformed thereon, said translucent reflective layer is made of an AgCucontaining alloy containing Cu the content of which is greater than orequal to 2.0 [atomic %] and less than or equal to 9.0 [atomic %], saidAgCu containing alloy is made of an AgCu containing either of ternaryalloy and quaternary alloy containing one or two chemical elements ofFe, Ni, Mo, W and whose total content of said chemical elements isgreater than or equal to 0.5 [atomic %] and less than or equal to 8.1[atomic %] and information is reproduced from said second informationrecording layer with irradiation of light that has passed through saidfirst information recording layer.
 5. (amended) In an optical recordingmedium including at least an information recording layer and areflective film, an optical recording medium characterized in that saidreflective film is formed of an AgCuPd containing alloy thin filmcontaining Cu the content of which is greater than or equal to 1.0[atomic %] and less than or equal to 8.2 [atomic %] and said AgCuPdcontaining alloy is made of an AgCuPd containing either of quaternaryalloy and quinary alloy containing one or two chemical elements of Al,Ti, Fe, Ni, Mo, W and whose total content of said chemical elements isgreater than or equal to 1.0 [atomic %] and less than or equal to 7.5[atomic %].
 6. (amended) In an optical recording medium in which atleast a first information recording layer and a second informationrecording layer are laminated to each other, an optical recording mediumcharacterized in that said first information recording layer has atranslucent reflective film formed thereon, said second informationrecording layer has a reflective film formed thereon, said translucentreflective film is made of an AgCuPd containing alloy containing Cu thecontent of which is greater than or equal to 1.0 [atomic %] and lessthan or equal to 8.2 [atomic %], said AgCuPd containing alloy is made ofan AgCuPd containing either of quaternary alloy and quinary alloycontaining one or two chemical elements of Al, Ti, Fe, Ni, Mo, W andwhose total content of said chemical elements is greater than or equalto 1.0 [atomic %] and less than or equal to 7.5 [atomic %] andinformation is reproduced from said second information recording layerwith irradiation of light that has passed through said first informationrecording layer.
 7. (amended) An optical recording medium according toclaim 2, 4 or 6, wherein said first information recording layer isformed on a first substrate, said second information recording layer isformed on a second substrate, said first and second substrates arelaminated to each other in such a manner that information recordinglayers thereof are facing to each other and information is reproducedfrom said first and second information recording layers with irradiationof light from said first substrate side.